Do I really want to save this marriage?

[brenalim]

This is the first marriage for us both. I'm 28 and he's 29 years old. No children.
He was involved with a woman for many years. He had intented on having "forever" with her when she was diagnosed with terminal cancer. When we met, he told me about her. He said that they were just friends now and he visited her often. We dated for two years and then he was offered a job out of state. He proposed and asked me to come with him. I was overjoyed and agreed.
Three months after moving, she passed away and that is when I started to notice a difference. He wasn't interested in having sex anymore. At first, I just let it go because I thought he was stressed out about the new job and morning the death of this woman. After several months, I tried to be positive and encouraging about it. I told him how great he was and how much I enjoyed being with him. When nothing improved after the wedding, I asked him if there was something I was doing wrong. Was it me? He said no and that it was just the natural progression of relationships. Sex once a month? I really hoped not.
Then I started doing research. I read everything I could get my hands on. I saw a therapist. I asked him to help me. I asked if he'd go see someone with me or alone, whichever he'd prefer. He agreed, but never went. I asked him again and again to help and he simply would not do it.
So naturally, I got angry and resentful. I never hid it from him. He'd ask and I'd tell him the truth. I stopped trying because it hurt so much to get turned down all the time, and I do mean all the time.
Two months ago, I discovered his affair. I didn't understand why he'd go to someone else for sex when I was right there. I'd never turned him down when he initiated (rarely) with me. He said that he'd go to therapy and we did. He said in therapy that when the woman in the beginning died, he felt guilty for moving on with his life and couldn't look at me the same anymore. I don't think he was truthful with me when he said they were "just friends." I asked him to give up his mistress and try to save our marriage and he said he would.
Now we're two months into this and he's still having the affair and still living with me (separate bedrooms) and we're going no where in therapy. I can't trust him when he's still cheating on me and he just can't seem to give her up.
This is what I know about the OW. She works with him, new to the office about 10 months ago. She's single. At the time of the affair, she'd just gotten out of a long term relationship. She hopes that "in the end, it'll all be worth it." (found that in a valentine's day card she sent my husband). She's a runner like my husband and she likes to snowboard, which my husband has recently taken up as a hobby. He used to be a skier. She's a spineless, soulless, husband stealing (insert bad word here).
How long am I supposed to wait? I'm honestly getting to the point where I want to raise a white flag. I don't know if I still want to save this marriage. He's not the man I thought he was and the more and more ambivalent he is, the more and more ambivalent I become.
I'm working with a DB coach and I'm working hard to take care of myself. It's a choice I have to make everyday and it's hard. He says the same things to her that he used to say to me. I thought I could forgive the infidelity in the beginning, but since he won't stop it, it's getting harder and harder to imagine our future together.
Other than take care of myself and do what makes me happy... what do I do? Please help!